1. Field of the Invention
The present invention relates to an actinic ray-sensitive or radiation-sensitive resin composition that when exposed to actinic rays or radiation (electron beams, X-rays, EUV, UV, etc.), makes a reaction to thereby have its properties changed and also relates to a method of forming a pattern by use of the composition. More particularly, the present invention relates to an actinic ray-sensitive or radiation-sensitive resin composition employed in a semiconductor production process for an IC or the like, a circuit board production process for a liquid crystal, a thermal head or the like and other photofabrication processes as well as in lithographic printing plates and thermosetting compositions, and also relates to a method of forming a pattern by use of the composition.
In the present invention, the terms “actinic rays” and “radiation” mean, for example, a mercury lamp bright line spectrum, far-ultraviolet rays represented by an excimer laser, extreme ultraviolet rays, X-rays, electron beams and the like. In the present invention, the term “light” means actinic rays or radiation.
2. Description of the Related Art
A chemical amplification resist composition is a pattern forming material that is capable of, upon exposure to far ultraviolet rays or other radiation, generating an acid at the exposed area and, by a reaction catalyzed by the acid, changing the solubility in a developer between the area having been exposed to actinic radiation and the nonexposed area to thereby attain pattern formation on a substrate.
In using a KrF excimer laser as an exposure light source, a resin whose fundamental skeleton consists of a poly(hydroxystyrene) exhibiting a low absorption mainly in the region of 248 nm is employed as a major component of the composition. Accordingly, there can be attained a high sensitivity, high resolving power and favorable pattern formation. Thus, a system superior to the conventional naphthoquinone diazide/novolak resin system is realized.
On the other hand, in using a light source of a further shorter wavelength, for example, an ArF excimer laser (193 nm) as an exposure light source, as the compounds having aromatic groups inherently exhibit a sharp absorption in the region of 193 nm, the above-mentioned chemical amplification system has not been satisfactory.
Therefore, resists for an ArF excimer laser containing a resin with an alicyclic hydrocarbon structure have been developed.
With respect to an acid generator being a major constituent of any of the chemical amplification resists, using a triphenylsulfonium salt as the same is generally known (see, for example, patent reference 1).
However, this acid generator is unsatisfactory in many respects. Accordingly, it is desired to develop a photosensitive composition enhanced in the sensitivity, resolution, pattern profile, roughness characteristic, etc. by improving the acid generator.
In particular, the roughness characteristic and resolution become important as the pattern dimension is reduced. Accordingly, in the lithography using X-rays, electron beams or EUV, as forming a pattern reduced to several ten nanometers is targeted, it is required to ensure excellence in especially the resolution and roughness characteristic.
When use is made of, for example, a light source emitting electron beams, X-rays or EUV, the exposure is carried out in vacuum. This would cause any low-boiling-point compounds, such as solvents, and resist materials decomposed by high energy to evaporate to thereby dirty the exposure apparatus. This outgas problem is attracting greater attention. In recent years, various researches have been made on the reduction of the outgas. The researches include a proposal to inhibit the evaporation of low-molecular compounds by providing a top coat layer (see, for example, patent reference 2) and a proposal to add a radical trapping agent for inhibition of any polymer decomposition (see, for example, patent reference 3). For the acid generator as well, an ingenuity for reduction of the outgas is demanded.